This disclosure relates to the layout and use of sub-resolution assist features.
Various systems may be used to print features such as patterns that define integrated circuits on semiconductor wafers. In general, electromagnetic wave emissions from a source are directed to expose selected locations on a substrate while leaving other locations unexposed. Example emissions include visible light, ultraviolet (UV) and extreme ultraviolet (EUV) radiation, and X-rays. These emissions all have characteristic wavelengths in various media.
Example approaches to directing these emissions toward selected locations include selective attenuation (e.g., using binary photomasks), interference (e.g., using phase shifting masks), reflection (e.g., using EUV reflective optical elements), and beam steering. Regardless of the approach used, systems for printing features have a resolution limit below which certain features are not resolved during printing.
Like reference symbols in the various drawings indicate like elements.